The idea with these riffs isn’t to play the whole song or that the suit the ukulele particularly well. It’s to throw them in to your playing for a bit of light relief and audience recognition (like the Ukulele Orchestra of Great Britain on Orange Blossom), to provoke the ‘I didn’t think you could play that on the ukulele’ or just for shits and gigs. Because of that, the riffs aren’t always arranged in the original key but the key that suits the ukulele best.